1. Field of the Invention
The present invention relates to lens barrel assemblies including lens barrels and lenses retained by the lens barrels, and more particularly, to a lens barrel assembly that can be manufactured at a low cost by forming a lens barrel by deep drawing.
2. Description of the Related Art
Lens barrel assemblies including cylindrical lens barrels and lenses retained by the lens barrels are known. An example of such a lens barrel assembly includes a lens barrel that is attached to a substrate such that the lens barrel covers an electric component, such as a semiconductor laser, provided on the substrate. The lens barrel assembly is used in an optical communication device to provide a function of, for example, emitting collimated light toward an isolator or collecting a laser beam at an end face of an optical fiber. The lens barrel included in the lens barrel assembly has a lens-retaining portion for retaining the lens at one of two open sides, and a component-receiving portion for receiving the electric component at the other open side. The lens-retaining portion and the component-receiving portion are formed integrally with each other. Japanese Patent No. 2878372 discloses an example of such a lens barrel assembly.
In commercialized lens barrel assemblies, the lens barrel is generally formed by a cutting process and the lens is formed in the lens barrel by a pressing process. In the case of forming the lens barrel by deep drawing a metal sheet, the lens-retaining portion and the component-receiving portion are formed to have substantially the same thickness, as described in Japanese Patent No. 2878372.
The outer diameter of the component-receiving portion is determined in conjunction with the diameter of a projection used in airtight welding and fixing. Therefore, it is difficult to change the outer diameter of the component-receiving portion. In addition, to ensure flexibility allowance for conductive wires connected to the electric component and work efficiency in the process of attaching the lens barrel, the inner diameter of the component-receiving portion can hardly be changed. Therefore, the thickness of the component-receiving portion is set to about 0.2 to 0.25 mm. As described above, the lens-retaining portion has the same thickness as that of the component-receiving portion.
In the process of molding the lens in the lens-retaining portion, a molding pressure is applied not only to the lens but also to the lens barrel. If the lens-retaining portion and the component-receiving portion have the same thickness as in the known structure, the lens-retaining portion cannot bear the molding pressure unless the outer peripheral surface of the lens-retaining portion is retained. Therefore, a mold having a complex structure is used to mold the lens. In addition, since the lens barrel is formed by a cutting process, high costs are incurred.